properties of iron and steels

8/10/2019 Properties of Iron and Steels

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GCSE Core Chemistry

Exam tip; You DO need to know the 3 main types of steel (carbon,low-alloy & high-alloy) & identify what they contain


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GCSE Core Chemistry


Keywords:Alloy, carbon steels, low-alloy steels, high-alloysteels

Prior Learning:

Identify & explain different extraction processes


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GCSE Core Chemistry


Learning Objectives:

By the end of the lesson I can:

The properties of pig iron and how this limits its usefulness.

Pig iron is the intermediate product o f smelt ing iron o re with

coke. Pig iron has a very hig h carbon content, typ ical ly 3.5

4.5%, which makes it very b ri t t le and not u seful direct ly as amater ial except for l im ited app l icat ions .

That iron can be alloyed to make it more useful.

Explain how the properties of alloys (but not smart alloys)

are related to models of their structures.


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GCSE Core Chemistry


What are the properties of different metals?


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GCSE Core Chemistry


gold (Au): This metal is unreactive. This is represented byhaving the band on stage, not mixing with the other elements

and not doing very much. lead (Pb), zinc (Zn) and copper (Cu): These metals are heavy

metals and are dressed up as heavy metal rockers.

copper (Cu): This metal has been drawn into wires.

aluminium (Al) and titanium (Ti): These metals are reactive.In this scene, they are getting overexcited and knocking over atable.

iron (Fe): This metal has rust patches and is struggling to liftthe bar stools.

steel (Fe wearing nerves of steel T shirts):These metalalloys have carbon atoms on their shoulders to show that theyare alloys. The steel is shinier than the iron atom. Steel is easilylifting the bar stools that iron was unable to lift because it isstronger.


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GCSE Core Chemistry


Lets go back in time 3 years to

Year 7

YEAR 10

YEAR 7

And draw (or

make a

model toshow) the

atom

arrangement

in a solid

Now add a

different

sized particleto your

model. What

is this

called?


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What are the general properties of most metals?

solid at room temperature

Why do metals have these particular properties?

high melting point

good conductors of electricity and heat

malleable: they can be shaped

ductile: they can be drawn into wires

strong

dense




sea of electrons

metal ions

The atoms in a pure metal are in

tightly-packed layers, which form

a regularlatticestructure.

The outer electrons of the metal

atoms separate from the atoms

and create a sea of electrons.

These electrons are delocalized

and so are free to move through

the whole structure.

The metal atoms become positivelycharged ions and are attracted to

the sea of electrons. This attraction

is called metallic bonding.




How does the sea of electrons affect the properties of metals?




Delocalized electrons in metallic bonding allow metals to

conduct heat and electricity.

This makes heat transfer in

metals very efficient.Delocalized electrons also

conduct electricity through

metals in a similar way.

For example, when a metal is

heated, the delocalized electrons

gain kinetic energy.

These electrons then move fasterand so transfer the gained energy

throughout the metal.

heat




Metals are usually strong, not brittle. When a metal is hit,

the layers of metal ions are able to slide over each other,

and so the structure does not shatter.

The metallic bonds do not break because the delocalized

electrons are free to move throughout the structure.

metal after it is hit

forceforce

This also explains why metals are malleable (easy to shape) and

ductile (can be drawn into wires).

metal before it is hit




E d k h f l (




Investigating Alloys

How would you investigate the strength of alloywires?

What will you change? (The independent variable)

What will you measure? (The dependent variable)

How would you make it a fair test? (Controlledvariables)

E D d k h 3 f l ( b




On a plain piece of paper add information

from the following slides to create a mindmap on iron including;

Alloying

Extraction

Properties

Chemical information

(Anything else you wish to include)

E i Y DO d k h 3 i f l ( b




Most iron is converted into

steels.

Removing all impurities wouldproduce pure iron. Pure iron has a

regular arrangement of atoms, with

layers that can slide over each

other, and so is soft and easily

shaped, but too soft for many uses.

The iron collected from a blast furnace is only

96% pure.

molteniron

hot air

moltenslag

raw materialsUsually, this product will be treated

further because the impurities make

iron brittle.

E ti Y DO d t k th 3 i t f t l ( b




Steel is an alloy of ironand other elements, including carbon,

nickel and chromium.

Steel is stronger than pure iron and can be used for

everything from sauce pans to suspension bridges!





The atoms of other elements are

different sizes. When other elementsare added to iron, their atoms distort

the regular structure of the iron atoms.

The atoms in pure iron are arranged

in densely-packed layers. These

layers can slide over each other. Thismakes pure iron a very soft material.

It is more difficult for the layers of iron

atoms in steel to slide over each other

and so this alloy is stronger than pure

iron.


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GCSE Core Chemistry


Steel is not a single substance & there are lots

of different steels all being an alloy of iron with

either carbon and/or other elements.

low carbon steelcontains less than 0.25% carbon

Soft and easily shaped. Not as strong as high carbon steel

but less likely to shatter.

high carbon steelcontains more than 0.5% carbon.

Very strong but brittle.

1. CARBON STEEL: made by alloying Fe

with small amounts of C (from 0.03-1.5%).

They are the cheapest to make & are used for

car bodies, knives, ships, machinery,containers, structural steel for buildings.

E m ti ; Y DO d t k th 3 m i t f t l ( b


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GCSE Core Chemistry


Nickel-steelvery resistant to

stretching forces so are used for long-

span bridges, military armour-plating

Tungsten-steeloperates well under very hot conditions so

it is used to make high-speed tools.

2. LOW-ALLOY STEEL: made by

alloying Fe with small amounts of other

metals (from 1-5%). They are moreexpensive & may contain metals like Ni,

Cr, Mn, V Ti and W. Each giving a

different property.

Exam tip; You DO need to know the 3 main types of steel (carbon


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GCSE Core Chemistry


Chromium-steelstrong withchemical stability it is mixed with

between 12-15% Cr and often some Ni

This is also known as stainless steelThese are used to

make cooking utensils & cutlery, chemical reaction vessels

because they combine hardness & strength with a resistance to

corrosion (they do not rust!)

3. HIGH-ALLOY STEEL: made by alloying

Fe with large amounts of other metals.

They are EVEN more expensive & maycontain metals like Ni, Cr, Mn, V Ti and W.

Each giving a different property.



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GCSE Core Chemistry




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GCSE Core Chemistry




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GCSE Core Chemistry


Refs Decision

If its true it stays, if its false SEND IT OFF!

Yellow = TRUE, Blue = FALSE

Steel is a mixtureAll steels contain cobalt (Co)

Stainless steels are expensiveStainless steels rust because

they contain iron

The molecular formula forsteel is St



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GCSE Core Chemistry


Learning Objectives:

By the end of the lesson I can: The properties of pig iron and how this limits its usefulness.

Pig iron is the intermediate product o f smelt ing iron o re with

coke. Pig iron has a very hig h carbon content, typ ical ly 3.5

4.5%, which makes it very b ri t t le and not u seful direct ly as amater ial except for l im ited app l icat ions .

That iron can be alloyed to make it more useful.

Explain how the properties of alloys (but not smart alloys)

are related to models of their structures.

properties of iron and steels

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